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Abstract:

There is provided a system that includes a power feed that distributes a
direct current (DC) voltage in a building. The DC voltage is In a range
of about 300-600 volts DC. The system also includes a motor, and a motor
drive. The motor drive receives the DC voltage via the power feed, and
from the DC voltage, derives an output that drives the motor.

Claims:

1. A system comprising:a power feed that distributes a direct current (DC)
voltage in a building, wherein said DC voltage is in a range of about
300-600 volts DC;a motor; anda motor drive that receives said DC voltage
via said power feed, and from said DC voltage, derives an output that
drives said motor.

2. The system of claim 1, further comprising:a first source of said DC
voltage; anda second source of said DC voltage,wherein said first source
and said second source are bridged together to provide said DC voltage to
said power feed.

3. The system of claim 1, further comprising:a sensor that senses a
parameter relating to an operation of said motor, and provides a
parameter value indicative thereof; anda controller that performs a
comparison of said parameter value to a reference value, and based on
said comparison, outputs a signal that controls said motor drive to, in
turn, control said output that drives said motor.

4. The system of claim 3,wherein said output of said motor drive is
related to a switching operation of a circuit of said motor drive,
andwherein said signal from said controller controls said switching
operation to control said output of said motor drive.

5. The system of claim 4, wherein said switching operation is selected
from the group consisting of a switching rate and a duty cycle.

6. The system of claim 4,wherein said motor is an alternating current (AC)
motor,wherein said output of said motor drive is an AC voltage,
andwherein said signal from said controller controls said switching
operation to control a frequency of said output of said motor drive.

7. The system of claim 4,wherein said motor is a DC motor,wherein said
output of said motor drive is a DC voltage, andwherein said signal from
said controller controls said switching operation to control a voltage
level of said output of said motor drive.

8. The system of claim 1, wherein said motor is a component of a piece of
equipment selected from the group consisting of a chiller, an air
conditioner, a fan, a pump and a compressor.

9. The system of claim 1,wherein said motor is a first motor, and said
motor drive is a first motor drive,wherein said system further
comprises:a second motor; anda second motor drive that receives said DC
voltage via said power feed, and from said DC voltage, derives an output
that drives said second motor, andwherein said first and second motors
are configured in a redundant relationship, and employed in a cooling
operation.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a highly reliable, redundant direct
current (DC) power system that provides modulated power to motors that
are utilized in the cooling of data centers and critical infrastructures.

[0003]2. Description of the Related Art

[0004]Critical infrastructures like data centers, telecommunications
center and others that require high density critical uptime power for
processing storage and communications have been steadily growing with
regard to their power and cooling requirements. In these critical
infrastructure applications, it is imperative to not only supply highly
reliable power, but also equally reliable cooling. If cooling were to
fail for even a small period of time the computer equipment could be
severely affected. Additionally, due to the extreme energy use of these
centers, it is imperative to design and apply systems that are not only
resilient but also highly efficient.

[0005]Traditionally, the power delivered to motors that provide the
movement of fluid and/or air in data centers has been provided by either
a utility company or by a stand-by generator when the utility is not
viable. With an increase in the power required to operate data center
equipment, and its associated heat, the necessity of providing
uninterruptible power to the pumps and fans motors during a power outage
has become a primary concern. While the alternating current (AC) power to
the computers in a data center is bridged by use of a battery backup
system during a utility outage, the essential motors pumps, fans and
compressors are typically allowed to go off line until a generator
assumes the load of the center. This process, from utility power outage
until the load is transferred to generators, can take up to 60 seconds
and in some cases longer, thereby leaving the critical cooling systems
off line for a dangerously long period of time. With the advent of
today's higher density data centers where the critical loads (processors,
storage and communications devices) are backed up by a battery system and
stay on line, the cooling systems do not stay online, potentially causing
the critical loads to overheat and in some instances damage occurs. It is
not prudent to place pumps, fans, compressors or motors on a dedicated
uninterruptible power supply system as the computing equipment may be
exposed to poor line quality and/or noise.

SUMMARY OF THE INVENTION

[0006]There is provided a system that includes a power feed that
distributes a direct current (DC) voltage in a building. The DC voltage
is in a range of about 300-600 volts DC. The system also includes a
motor, and a motor drive. The motor drive receives the DC voltage via the
power feed, and from the DC voltage, derives an output that drives the
motor.

[0008]FIG. 1 is a schematic of a redundant DC power system, i.e., system
100. System 100 is configured as a 2N power system, where N is the amount
of power required to properly support power loads. System 100 includes
generators 101A, B, rectifiers 105A, B, motor drives 111A, B, motors
113A, B, sensors 150A, B, and a controller 155.

[0010]System 100 receives alternating current (AC) from utilities 102A, B.
The AC current from utility 102A is coupled through a breaker 122A, and
the AC current from utility 102B is coupled through a breaker 122B.
Breakers 122A, B protect circuits downstream of breakers 122A, B, and can
be implemented as either circuit breakers or fuses.

[0011]Generator 101A provides emergency power in a case of a power outage
of utility 102A. Generator 101A is configured as a combination of an
engine, for example, a diesel engine 123A coupled to an energy storage
device 124A, e.g., a flywheel, that is in turn coupled to a synchronous
motor 125A. Diesel engine 123A is an energy source that, when engaged,
generates an AC output. Energy storage device 124A captures energy in the
form of the AC output of the diesel engine 123A, and holds this energy in
reserve for discharge at an onset of a power emergency. Synchronous motor
125A is essentially a generator which provides an AC voltage that is
stepped up to a higher AC voltage, e.g., 13 KV, through a step-up
transformer 126A.

[0012]Generator 101B provides emergency power in a case of a power outage
of utility 102A, and is configured as a combination of a diesel engine
123B coupled to an energy storage device 124B, that is in turn coupled to
a synchronous motor 125B. The output of synchronous motor 125B is stepped
up through a step-up transformer 126B. Generator 101B, diesel engine
123B, energy storage device 124B, synchronous motor 125B, and step-up
transformer 126B function similarly to generator 101A, diesel engine
123A, energy storage device 124A, synchronous motor 125A, and step-up
transformer 126A, respectively.

[0013]A tapped choke 103A couples power from either utility 102A or
step-up transformer 126A to a load downstream of tapped choke 103A. When
power is available from utility 102A, tapped choke 103A couples power
from utility 102A. When a power outage of utility 102A occurs, tapped
choke 103A uncouples utility 102A from the load and, and instead,
receives power from step-up transformer 126A. Similarly, a tapped choke
103B receives power from utility 102B and step-up transformer 126B, and
couples the power to a load downstream of tapped choke 103B.

[0015]As mentioned above, if utilities 102A, B are not available, the
power will be delivered to rectifiers 105A, B from generators 101A, B,
respectively. Generators 101A, B can be various sizes and voltages
necessary to match the characteristics of the utility 102A, B normally
feeding the inputs of rectifiers 105A, B.

[0016]Rectifiers 105A, B utilize power from utilities 102A, B or
generators 101A, B and rectify such power to provide a DC output, e.g.,
300-600 volts DC (VDC). The DC output of rectifier 105A is coupled
through a diode 108A and a breaker 106A to a bus 109. Similarly, the DC
output of rectifier 105B is coupled through a diode 108B and a breaker
106B to bus 109. Breakers 106A, B protect circuits downstream of breakers
106A, B, and may be implemented as either circuit breakers or fuses.

[0017]Rectifiers 105A, B each include an electrical filter (not shown) on
the input side of rectifiers 105A, B to reduce a negative effect of
reflected harmonics onto bus 109, motor drives 111A, B, motor 113A, B or
motor controller 155. Output stabilization of the DC output rectifiers
105A, B will also be passively attenuated by a capacitance and an
inductance in the form a tuned filter within the DC outputs of rectifiers
105A, B.

[0018]The DC outputs of rectifiers 105A, B are "OR-gated" or bridged
together through diodes 108A, B to bus 109. That is, power can be
supplied to bus 109 by either rectifier 105A or rectifier 105B, or by
both of rectifier 105A and rectifier 105B simultaneously.

[0019]In addition, each of rectifiers 105A, B have a control panel (not
shown) that provides an operator with the ability to change the DC output
voltages of rectifiers 105A, B. This allows for the DC output voltages of
rectifiers 105A, B to be varied so that either rectifier 105A or
rectifier 105B can supply a higher voltage than the other rectifier
105A,B, thus allowing the highest of the two voltages to feed bus 109,
and the lowest of the two voltages to become a secondary redundant feed
if the highest feed were to fail. Rectifiers 105A, B can be applied
either as a unit of one or in units of two or more (parallel) to produce
greater amounts of power or redundancy.

[0020]System 100 also includes diodes 118A, B, chargers 117A, B, batteries
116A, B, diodes 115A, B, and breakers 114A, B. During normal operation of
rectifier 105A, DC current flows through diode 118A to charger 117A,
which, in turn, charges battery 116A. Diode 108A and diode 115A "OR" the
outputs of rectifier 105A and battery 116A. In a case of a loss of power
from rectifier 105A, battery 116A provides DC power through diode 115A
and breaker 114A, to bus 109. Similarly, during normal operation of
rectifier 105B, DC current flows through diode 118B to charger 117B,
which, in turn, charges battery 116B. Diode 108B and diode 115B "OR" the
outputs of rectifier 105B and battery 116B. In a case of a loss of power
from rectifier 105B, battery 116B provides DC power through diode 115B
and breaker 114B, to bus 109.

[0021]Batteries 116A, B, by way of example, can be any energy storage
vehicle such as a kinetic flywheel, a fuel cell, or a capacitor. Breakers
114A, B protect circuits downstream of breakers 114A, B, and may be
implemented as either circuit breakers or as fuses.

[0022]Bus 109 is routed as a DC power feed that provides a DC voltage,
e.g., 300-600 VDC, in a building. That is, bus 109 is routed through the
building so that devices or subsystems that require DC power can obtain
the DC power via bus 109.

[0024]A switch 109A enables the isolation of rectifier 105A and motor
drive 111A from rectifier 105B and motor drive 111B for service or
maintenance. More specifically, when switch 109A is opened circuitry on
the left side of switch 109A, e.g., rectifier 105A and motor drive 111A,
is isolated from circuitry on the right side of switch 109A, e.g.,
rectifier 105B and motor drive 111B.

[0025]As mentioned above, the outputs of rectifiers 105A, B, are
"OR-gated" For example, assume that rectifier 105A is higher in voltage
than rectifier 105B, and that switch 109A is closed. Because switch 109A
is closed, current from diode 108A feeds motor drives 111A and 111B. If
the voltage from rectifier 105A drops to a voltage equal to that of
rectifier 105B, rectifier 105B will share the load equally with rectifier
105A. If the voltage from rectifier 105A drops below that of rectifier
105B, rectifier 105B will feed motor drives 111A, B.

[0027]Motors 113A, B are installed in equipment such as chillers, computer
room air conditioners, fans, pumps or compressors, and are utilized to
move air, water or any other cooling medium. Motors 113A, B can be
installed separately from one another, or be used together to provide
redundancy in a piece of equipment or redundancy in an environment that
requires critical cooling. For example, with regard to the redundancy,
motors 113A and 113B can both be situated in a computer room so that if
either motor 113A or motor 113B fails, the other motor 113A or 113B will
still be available.

[0028]Motors 113A, B can be either DC motors or AC motors. A DC motor's
speed and torque is directly related to its input voltage. The greater
the voltage the faster the speed, and the lower the voltage the slower
the speed. Thus, the speed of a DC motor is controlled by varying the
input voltage to the DC motor. An AC motor's speed is directly related to
its input voltage frequency. The higher the frequency the faster the
speed, and the lower the frequency the slower the speed. Thus, the speed
of an AC motor is controlled by varying the frequency of the input
voltage to the AC motor.

[0029]In a case where motor 113A is a DC motor, motor drive 111A will
provide a DC voltage to motor 113A. In a case where motor 113A is an AC
motor, motor drive 111A will provide an AC voltage to motor 113A.
Similarly, motor drive 111B will drive motor 113B with either a DC
voltage or an AC voltage.

[0030]Sensor 150A senses a parameter relating to the operation of motor
113A, and outputs a parameter value 152A indicative thereof. The
parameter can be any suitable parameter, but examples include (i) speed
of motor 113A, and (ii) temperature of an environment being cooled by a
cooler that is driven by motor 113A. Similarly sensor 150B senses a
parameter relating to the operation of motor 113B, and outputs parameter
value 152B. Controller 155 monitors parameter values 152A and 152B, and
controls motor drives 111A, B so that parameter values 152A and 152B are
maintained within a desired range.

[0031]When motor 113A is a DC motor, motor drive 111A is implemented as a
DC to DC motor drive, and controller 155 causes the output voltage of
motor drive 111A to vary, to control motor 113A. The output voltage range
of motor drive 111A may be any suitable range, but exemplary ranges are
0-300 VDC or 0-600 VDC. When motor 113A is an AC motor, motor drive 111A
is implemented as a DC to AC motor drive, and controller 155 causes the
output frequency of motor drive 111A to vary, to control motor 113A. The
output frequency may be any suitable range, but an exemplary range is
0-60 Hertz (Hz).

[0032]The output of motor drive 111A is varied by controlling a switching
operation, e.g., switching rate or duty cycle, of a circuit contained
therein. The circuit can be implemented, for example, using an insulated
gate bipolar transistor (IGBT), a silicon controlled rectifier (SCR), or
a metal oxide semiconductor field effect transistor (MOSFET).
Accordingly, controller 155 provides a control signal 130A to motor drive
111A to vary the switching rate or duty cycle, thereby adjusting the
output voltage or frequency from motor drive 111A, and thus the rate of
change and speed of motor 113A. The speed and torque of motor 113A
produces an amount of work. A parameter relating to this work is sensed
by sensor 150A and parameter value 152A is transmitted to controller 155.

[0034]Controller 155 includes a processor 157 and a memory 160 that
contains a module of instructions, e.g., program 170, for controlling
processor 157. Memory 160 also contains a reference value 165A and a
reference value 165B for parameter values 152A and 152B, respectively.
With regard to the operation of motor 113A, controller 155, and more
particularly, processor 157, compares parameter value 152A to reference
value 165A, and based on a result of the comparison, sends control signal
130A to motor drive 111A, which, in turn, adjusts the speed of motor 113A
so that parameter value 152A satisfies reference value 165A. Similarly,
controller 155 compares parameter value 152B to reference value 165B, and
based on a result of the comparison, sends control signal 130B to motor
drive 111B, which, in turn, adjusts the speed of motor 113B so that
parameter value 152B satisfies reference value 165B.

[0035]For example, assume that motor 113A drives a compressor in an air
conditioner in a room. Sensor 150A senses a temperature of the room and,
in the form of parameter value 152A, reports the temperature to
controller 155. Controller 155 compares the sensed temperature to a
reference value, e.g., reference value 165A, and based on the comparison,
sends control signal 130A to motor drive 111A. Motor drive 111A, in
response to control signal 130A, adjusts an operation of motor 113A so
that the temperature in the room does not exceed the reference value.

[0036]Although controller 155 is described herein as having program 170
installed into memory 160, program 170 can be embodied on a storage media
175 for subsequent loading into memory 160. Storage media 175 can be any
computer-readable storage media, such as, for example, a floppy disk, a
compact disk, a magnetic tape, a read only memory, or an optical storage
media. Program 170 could also be embodied in a random access memory, or
other type of electronic storage, located on a remote storage system and
coupled to memory 160.

[0037]Also, although program 170, reference value 165A and reference value
165B are described herein as being installed in memory 160, and therefore
being implemented in software, they could be implemented in any of
hardware, firmware, software, or a combination thereof.

[0038]The techniques described herein are exemplary, and should not be
construed as implying any particular limitation on the present invention.
It should be understood that various alternatives, combinations and
modifications could be devised by those skilled in the art. The present
invention is intended to embrace all such alternatives, modifications and
variances that fall within the scope of the appended claims.